1. Field of the Invention
The present invention relates generally to high resolution imaging, and more specifically to high resolution imaging of objects using sources of ionizing radiation.
2. Description of the Background Art
A variety of methods exist for imaging objects using UV, x-ray, and other ionizing radiation sources. These methods have used photographic films, phosphor screens in conjunction with CCD cameras, and thermoluminescent or optically stimulable luminescent phosphor powders in conjunction with a scanning laser readout system. In these techniques, the dimensions of the photosensitive grains in the film or phosphor and scattering effects limit the obtainable resolution. Grain sizes in typical phosphors are on the order of tens of microns, and crushing the phosphor to sub micron dimensions often results in a loss of phosphor activity. Grain sizes in photographic films range from 0.15 .mu.m.sup.2 for very slow speed (low sensitivity) film to 2.6 .mu.m.sup.2 for very high speed (high sensitivity) film. For film, the resolution is from 10 to 100 times the grain size because of the chemistry involved in the developing process. Problems with photographic films include the necessity for chemical developing, nonlinear response, limited dynamic range and single use. The resolution for direct imaging using a CCD camera is determined by the individual pixel size of the CCD array and the magnification factor used for collecting the image. Modern CCD cameras have pixel dimensions of approximately 8 .mu.m.times.8 .mu.m.